Positive displacement sortation conveyors are known having a main conveying surface and diverter shoes, or pusher shoes, that are generally used to displace articles laterally on the main conveying surface, such as when the articles are to be diverted upon one or more spur conveyor lines typically placed at an angle to the main conveying surface. Such conveyors may include a pair of endless chains or other connecting members and a plurality of members, such as slats, connected at their opposite ends to the chains or connecting members in order to provide a moving conveyor surface. Each slat, or a pair of slats, is fitted with a pusher or diverter shoe mounted in a manner such that the shoe moves laterally across the slat or slats. Movement of the shoe is guided by a guide track beneath the conveying surface. At the loading end of the sortation system, the shoes have a particular orientation with respect to the conveying surface. When an article is to be diverted to a particular spur line, a diverter assembly is actuated to switch shoes adjacent the article onto one or more diagonal tracks causing the effected shoes to glide across the slats to divert the article. Examples of such positive displacement sorters include commonly assigned U.S. Pat. Nos. 4,738,347 and 5,127,510. Other examples include U.S. Pat. Nos. 3,361,247; 5,409,095; and 4,884,677; and European Published Pat. Application Nos. EP 0 602 694 B1 and EP 0 444 734 A1.
As such positive displacement sorters increase in speed in order to handle increasing article, or product, throughput, lateral acceleration of the article by the pusher shoe can have detrimental effects. Such effects include, by way of example, tipping of the article, skewing of the article, ballistic separation of the article from the pusher shoe, and the like.